Debugging Embedded Systems Requirements Before The Design Begins

Abstract

Over the last two decades, there has been a real movement towards requirements engineering [1]. However, the various tools that have been developed with the aim of improving the specifications development are mostly focused on requirements management and traceability, and there was no easy-to-use requirements validation tool available for checking their functional consistency before any design or coding takes place. As a result, 40 to 60% of design bugs are caused by faulty requirements that generate costly iterations of the development process. Argosim's ambition is to change this situation by providing STIMULUS [2], the very first requirements simulation tool for real-time embedded systems. STIMULUS combines the ability to write requirements into a formal yet simple textual language, but also and even more importantly, to simulate them by generating the possible behaviours of the specified system in the form of execution plots. The analysis of simulation results allows for the quick and early detection of ambiguous, incorrect, incomplete or even conflicting requirements. In practice, STIMULUS integrates seamlessly into the agile development processes [3]. It allows for the concurrent development and validation of both the requirements and their test scenarios in a very incremental way. Once validated at the specification level, both requirements and test scenarios can be reused to validate the design implementation.Test scenarios make it possible to generate many test vectors automatically, while requirements are reused as test observers, or test oracles, in order to automatically check that the system satisfies its requirements. This paper describes the major innovation offered by STIMULUS in the field of requirements engineering. It will first present its operating principles and then briefly illustrate both the requirements validation and software validation workflows with an example from the automotive domain.